LED (light emitting diode) is a semiconductor device that emits light when an electric current passes through it. This technology utilizes an effect called “electroluminescence” to generate light. This is distinctly different, and far more efficient, than traditional incandescent technology which utilizes heat to generate light. LED light bulbs last 40X longer than incandescent light bulbs.
See an example of how cities are using LED’s to save money here.